This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-221836, filed Jul. 30, 2002, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a projection display device which projects optical images onto a screen for image reproduction and more specifically to improvements in means for cooling light bulbs used in the display device. Also, the present invention relates to improvements in air blowing device suitably used to cool the light bulbs of a projection display device such as a liquid crystal projector.
2. Description of the Related Art
As is well known, information terminals for home use, such as personal computers, have come into wide use in recent years. Moreover, high-definition television has also started. Under these circumstances, the demand has increased for reproducing images on a larger screen with higher brightness and quality.
To meet such a demand, the development of projection display devices, such as liquid crystal projectors, is accelerated at present. In the projection display device, light from a light source is decomposed into three primary color components of red (R), green (G) and blue (B) and each colored light is then directed onto a corresponding one of the liquid crystal light panels.
Each of these light panels is driven by a respective one of the R, G and B image signals to produce image light modulated by the image signal. The rays of image light output from the liquid crystal light panels are combined and then enlargement projected through a projection lens onto a screen for image reproduction.
In this type of projection display device, as its light source use is frequently made of a lamp of high power dissipation, such as a metal halide lamp or extra-high pressure mercury lamp. For this reason, it is required to make provisions not only for cooling the interior of the device or cooling for increasing the life of the lamp itself but also for cooling the interior of the optical engine.
The cooling of the interior of the optical engine is performed mainly on polarization conversation elements, input and output polarizing plates, and the liquid crystal light panels. In many cases, these parts, unlike lenses and mirrors, are not composed of inorganic materials only. When the parts rise in temperature, not only is their life shortened, but also the performance required of them as products cannot be maintained.
The parts inside the optical engine are required to allow incoming light to pass through. For this reason, with a cooling method using heatsinks, it is impossible to secure a large contact area, thus reducing the cooling efficiency. Thus, forced-air cooling using air blowers (fans) is generally adopted.
At present, with reduction in dimensions of projection display devices and increase in the luminance, downsizing of optical parts and increasing of the output power of light sources are in progress. Under these circumstances, cooling of the input and output polarizing plates and the liquid crystal light bulbs in particular has become further difficult.
As provisions for cooling, various methods have been developed which include a method which uses a centrifugal fan with higher static pressure in place of an axial fan, a method which uses a material of high heat transfer rate for the glass that is used for lamination of polarizing plates, and a method which uses a material of high heat transfer rate for a frame that holds a liquid crystal light bulb.
To lower the temperature of parts to be cooled, the speed of the fan is simply increased to increase the quantity of air, in which case noise involved in increasing the quantity of air will become a problem. For this reason, the important issue is how to lower ventilation resistance associated with the paths from the fan to the input and output polarizing plates and the liquid crystal light bulbs.
Ideally, it is the most effective to apply air directly from the fan to the parts to be cooled without providing air ducts. In practice, however, structural restrictions resulting from downsizing of the device frequently cause it to have to take the configuration in which airflow is conducted from the fan through air ducts to the parts to be cooled.
In this case, if the air duct is bent, there will be produced nonuniformity in the quantity of air finally blown out of the outlet of the air duet. For this reason, the input and output polarizing plates and the liquid crystal light panel will each have sufficiently cooled portions and insufficiently cooled portions. This has an adverse effect on the quality of a displayed image.
To cope with this problem, for example, Jpn. Pat. Appln. KOKAI Publication No. 11-82393 discloses a configuration which causes a fan to take in air uniformly therethrough to thereby allow the quantity of air sent out by the fan to become uniform.
With this disclosed configuration, however, it is required to blow air directly from the fan onto the parts to be cooled. This makes it necessary to place the fan in the proximity of the input and output polarizing plates and the liquid crystal light panel. The configuration is therefore not suited for use with projection display devices with downsizing requirements.
According to an aspect of the present invention, there is provided a projection display device comprising: a light source, a display section configured to receive light from the light source and output image light modulated with an image signal; a projection device configured to project the image light output from the display section; a duct device having an air duct for conducting air from an air intake to an air discharge section and an air chamber which is formed downstream of the air discharge section in the air duct and configured such that cooling air blows from the air discharge section toward the display section; and an air blower configured to blow cooling air into the air intake.
According to another aspect of the present invention, there is provided an air blowing device which blows cooling air against a part to be cooled comprising: a duct device having an air duct for conducting air from an air intake to an air discharge section and an air chamber formed downstream of the air discharge section in the air duct and configured to blow cooling air from the air discharge section toward the part to be cooled; and an air blower configured to blow cooling air into the air intake.